Gas cooktop burner



FIG. 1 is a perspective view of a gas cooktop burner showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a left view thereof;

FIG. 4 is a front view thereof; and,

FIG. 5 is a right view thereof. 

The ornamental design for a gas cooktop burner, as shown and described. 